The present invention relates to preforming apparatus for a stranding machine, in particular apparatus for the preforming of wires and strands directly ahead of the stranding point in stranding machines.
It is known that wires or strands during the production of ropes experience a twisting around the insert, which has the consequence that the wires in the finished rope are disposed under appreciable stress. When such a rope is cut through, the rope end unravels and forms a so-called brush.
Different methods are known for countering this stress, for example, preforming of the wires. In this method, the wires are deformed beyond the elastic limit into a wave shape by a suitable preforming device arranged immediately ahead of the stranding point. Since this wave-shaped deformation takes place in the running wire, the main axes of which (vertical and horizontal) are not tilted during the rotary motion of the ropes for the stranding process but are merely displaced parallel to one another, the wire is provided with a spatial wave shape, i.e. a helical shape, which corresponds to the shape the wire assumes in the finished rope, which results in an appreciable reduction of the above-mentioned stress.
The deformation of the wire is produced in the preforming apparatus by guiding the wire over two or three rollers, which are journalled overhung and which are adjustable in their spacings or lateral settings relative to each other. There are two different kinds of preforming apparatus known, in one of which the axes of the rollers in the longitudinal direction of the stranding machine are aligned with a slight inclination to the central axis and in the other one of which the axes of the rollers extend transversely to the longitudinal direction of the stranding machine and thus run perpendicularly to the central axis, but at a lateral spacing therefrom.
The present invention concerns preforming apparatus of the last-mentioned kind, in which the roller axes are perpendicular to and spaced from the axis of the machine. The known devices of this kind as a rule consist of three rollers, with the wires running through between the rollers. The actual helical shape of the wire is in that case dependent on, apart from the diameter of the rollers, how closely the rollers are to one another and how deeply the middle roller is pushed in between the other two rollers. When the helical shape of the wire is to be altered, two resetting processes are necessary: on the one hand, the spacing of the outer rollers must be reset, and, on the other hand, the depth of the middle roller must be reset.
Since wire ropes now generally consist of six, eight or even more individual or stranded wires, the stranding machines thus have six, eight or more spools and there must also be present six, eight or more preforming devices, since each wire or each strand must be individually deformed.
It is a disadvantage of the known preforming apparatus of this kind that each of the preforming devices must be individually adjusted when a new setting is necessary. While it is relatively simple and in fact known to provide a common resetting device for all the preforming devices in preforming apparatus with roller axes extending in the direction of the machine axis but somewhat inclined thereto, the possibility of common resetting has hitherto been absent in apparatus having preforming devices with roller axes extending transversely to the machine axis.
It is, therefore, the object of the present invention to provide a common resetting mechanism also in preforming devices having roller axes extending transversely to the machine axis.